Squalene and botryococcene are related by their putative biosynthetic origins from the condensation of two farnesyl diphosphate (FPP) molecules, a common biosynthetic intermediate found in the mevalonate biosynthetic pathway, and are known to be synthesized by Botryococcus braunii, race B, a fresh water algae (Okada et al., J. Appl. Phycology, 7: 555-559, 1995; Metzger et al., Appl. Microbiol. Biotech., 66: 486-496, 2005). Botryococcus braunii is known for its ability to accumulate large amounts of hydrocarbons. In particular B. braunii race B can accumulate 20-50% its dry weight of C30-C34 botryococcenes and squalenes.
Squalene, botryococcene and their methylated derivatives from B. braunii have attracted significant attention because these molecules are thought to be the progenitors to current oil shale deposits (Summons et al., Organic Geochem., 33: 99-109, 2002; Walters et al., AAPG Bulletin, 89: 1239-1244, 2005) and because they are considered promising renewable, alternative biofuels (Banerjee et al., Crit. Rev. Biotech., 22: 245-279 (2002)). For example, Hillen et al. (Biotech. Bioeng., 24: 193-205, 1982) previously reported on the catalytic cracking of oils extracted from Botryococcus braunii, primarily the methylated botryococcenes and squalene derivatives, and observed an overall conversion of 79% of the oil to combustible fuels under standard cracking conditions. Overall, 67% of the converted oil was to gasoline grade fuel (octanes), 15% to aviation turbine fuel, and 15% to diesel fuel with a residual of only 3%. Hence, catalytic hydrolysis (as performed in standard petroleum refineries) of these highly branched, poly-unsaturated triterpenes results in the generation of hydrocarbon fractions that are chemically equivalent to those derived from current petroleum deposits and are of direct utility as fuels for internal combustion engines, as well as feedstocks for chemical manufacturing (Banerjee et al., 2002).
These energy-rich triterpene oils have only been available from cultures of Botryococcus braunii, a rather slow growing green algae that does not lend itself to large-scale or fermentation type culturing conditions (Casadevall et al., Biotech. Bioeng., 27: 286-295 (1985)). Thus, there is a need for improved sources of these energy-rich triterpene oils.